Metal Injection Molding (MIM) is a new kind of Powder metallurgy technology, which is developed from powder injection molding (PIM) of ceramic parts. The main production steps of Metal Injection Molding are as follows: mixing of metal powder and binder-granulation-injection molding-degreasing-sintering-subsequent treatment-final product, the technology is suitable for small, complex, high-performance mass production Powder metallurgy parts, such as those used by the Swiss watch industry to make watch parts. In recent decades, MIM technology has developed rapidly, the applicable materials include: Fe-Ni alloy, stainless steel, tool steel, high specific gravity alloy, cemented carbide, titanium alloy, ni-based superalloy, intermetallic compound, alumina, zirconia and so on. Metal Injection Molding (MIM) technology requires that the particle size of the powder is less than micron and the shape is nearly spherical. In addition, loose density, vibrating density, ratio of length to diameter, natural slope angle and particle size distribution are also required. At present, the main methods of producing powder for metal injection molding technology are water atomization, gas atomization and carbonyl group method. The commonly used powder brands for injection of stainless steel metals are: 304L, 316L, 317L, 410L, 430L, 434L, 440A, 440C, 17-4PH, etc. . The process of water atomization is as follows: selection of stainless steel raw material-melting in medium frequency induction furnace-composition adjustment-deoxidation and slag removal-atomization and pulverization-quality detection-screening-packaging and storage, the main equipment used are: medium-frequency induction furnace, high-pressure water pump, closed pulverizing device, circulating water tank, screening and packaging equipment, testing equipment.
The process of gas atomization is as follows:
selecting stainless steel raw material-melting in medium frequency induction furnace-composition adjustment-deoxidation and slag removal-atomization and pulverization-quality detection-screening-packaging and storage. The main equipment used are: medium frequency induction melting furnace, nitrogen source and atomization device, circulating water tank, screening and packaging equipment, testing equipment. Each method has its own advantages and disadvantages: Water Atomization is the main pulverizing process, its high efficiency, large-scale production is more economical, can make the powder fine, but the shape is irregular, which is conducive to shape preservation, but the binder used more, affect the accuracy. In addition, the oxidation film formed by the reaction of water and metal at high temperature hinders sintering. Gas Atomization is the main method to produce powder for metal injection molding technology. The powder produced by gas atomization is spherical, with low oxidation degree, less binder needed and good formability, but the yield of ultra-fine powder is low, the price is high and the shape keeping property is poor, c, N, H, O in binder have effect on sintered body. The powder produced by carbonyl method is high in purity, stable at the beginning and very fine in particle size. It is most suitable for MIM, but only for Fe, Ni and other powders, which can not meet the requirements of varieties. In order to meet the requirements of powder for metal injection molding, many companies have improved the above methods and developed micro-atomization and laminar atomization methods. Now it is usually water atomized powder and gas atomized powder mixed use, the former to improve the density of compaction, the latter to maintain the shape. At present, using water atomizing powder can also produce sintered body with relative density more than 99% , so only water atomizing powder is used for larger parts, and gas atomizing powder is used for smaller parts. In the past two years, Handan Rand Atomizing Pulverizing Equipment Co. , Ltd. has developed a new type of atomizing pulverizing equipment, which can not only ensure the large-scale production of water atomizing and the ultrafine powder, but also take into account the advantages of the spherical powder shape.
Post time: Oct-24-2022
